The present invention relates to the locking of a nozzle tip within a nozzle tip housing of a mold.
Molds which are used to injection mold plastic parts include nozzle tips held within a nozzle tip housing of the mold. These nozzle tips are generally threaded into position which then enables them to be unthreaded from the mold for purposes of maintenance, cleaning, replacement etc.
Although the threaded securing of the nozzle tip within the housing has the benefits noted above, it also results in some disadvantages. Most particularly, the nozzle tip has a tendency, under operating pressures of the mold, to inadvertently unthread from its housing. This unthreading is typically not noticeable from a visual stand point but is sufficient to adversely affect the accuracy of the mold.
The prior art does teach some answers to this unthreading problem. For example, it is known to thread a separate locking nut into the housing over the threaded base of the nozzle tip. However, this arrangement suffers from its own drawbacks including the fact that the separate locking nut can itself prematurely release and further that the use of the nut necessitates substantial revisions to the nozzle tip housing. All of this makes the modification to the mold quite sizable, complicated and costly.
The present invention relates to a mold assembly including a nozzle tip locked into its housing by means of a relatively small inexpensive yet effective locking member which necessitates very little in the way of modification to either the nozzle tip or the nozzle tip housing.
More particularly, a mold assembly according to the present invention comprises a nozzle tip having a threaded base which secures within a threaded socket of a hollow stem of a nozzle tip housing. The nozzle tip includes an outwardly projecting shoulder and the hollow stem of the housing has an internal recess for purposes it be described immediately below.
The assembly further includes a locking member having both internal and external projections. The locking member fits over the nozzle tip with the external projection of the locking member located within the internal recess of the housing stem and with the outwardly projecting shoulder of the nozzle tip trapped by the internal projection of the locking member to block unthreading of the nozzle tip from the housing.